package l.l.w.practice.校招全国统一模拟笔试第五场编程题集合2017年.制造回文;

import java.util.Scanner;

/**
 * Created by llw on 2017/10/13.
 */
public class 制造回文 {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        int result = new 制造回文().getNum(str);
        System.out.println(result);
    }

    public int getNum(String str) {
        int result = 0;
        int[] nums = new int[26];
        for(int i = 0 ;i < str.length(); ++i){
            int index  = str.charAt(i)-'a';
            nums[index] = nums[index] +1;
        }
        for(int j =0; j < 26; ++j){
            if((nums[j] & 1)==1){
                result++;
            }
        }
        return result;
    }
}
